Electronic excitation spectra of cerium oxides: from <i>ab initio</i> dielectric response functions to Monte Carlo electron transport simulations

Pedrielli, Andrea; Vera, Pablo de; Trevisanutto, Paolo E.; Pugno, Nicola; García-Molina, Rafael; Abril, Isabel; Taioli, Simone; Dapor, Maurizio

doi:10.1039/d1cp01810h

Cited by 12 publications

(13 citation statements)

References 86 publications

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“…Theoretical calculations propose a strong ionic character for stoichiometric CeO 2 and substoichiometric CeO 2-d concomitant with a low orbital overlap in the O 2p region located in the valence band. 16,18,19 The density of states (DOS) of Ce 4f and Ce 5d inside the O 2p region is extremely low, generally associated with electronic tails or reminiscent states, giving a strong O 2p character to CeO 2 and CeO 2Àd . However, this is valid only from a theoretical point of view, as an increase in intensity will be observed if these theoretical states are normalized by the experimental photoionization cross-section (PICS) at 21.2 eV.…”

Section: Resultsmentioning

confidence: 99%

“…1). 16,17 The reducibility of CeO 2 is facilitated by the electron transition (occupied) O 2p -(unoccupied) Ce 5d and Ce 4f 18 concomitants with the release of two electrons from O 2À anions, leading to the formation of two Ce 3+ cations. The ionic character of ceria foresees a low degree of hybridization between Ce 5d, O 2p, and Ce 4f occupied states.…”

Section: Introductionmentioning

confidence: 99%

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Unraveling Ce³⁺ detection at the surface of ceria nanopowders by UPS analysis

Cárdenas

Molinet--Chinaglia

Loridant

2022

Phys. Chem. Chem. Phys.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Unraveling Ce³⁺ detection at the surface of ceria nanopowders by UPS analysis

Cárdenas

Molinet--Chinaglia

Loridant

2022

Phys. Chem. Chem. Phys.

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“…Even though the Random Phase Approximation (RPA) (

) provides a reasonable estimation of the macroscopic dielectric matrix, ALDA calculations have shown a general improvement in the agreement with the Inelastic X-Ray Scattering (IXS) experimental results, not only in finite-systems but also in crystalline systems [ 71 , 72 , 73 , 74 , 75 ]. This good TD-LDA (TD-DFT with ALDA kernel) behaviour in describing the IXS is commonly due to the less prominence of excitonic effects in the ELF in contrast to the absorption spectra (the ALDA and APBE omit the ultra-nonlocal term fundamental to represent them in the macroscopic limit, see Ref.…”

Section: Methodsmentioning

confidence: 99%

“…The energy loss function is then given by

. The off-diagonal elements of the dielectric matrix are responsible for the Local Fields Effects (LFEs) and become essential in inhomogeneous systems where localisation of atomic orbitals plays a significant role [ 75 ].…”

Section: Methodsmentioning

confidence: 99%

Energy Deposition around Swift Carbon-Ion Tracks in Liquid Water

Vera

Taioli

Trevisanutto

et al. 2022

IJMS

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Energetic carbon ions are promising projectiles used for cancer radiotherapy. A thorough knowledge of how the energy of these ions is deposited in biological media (mainly composed of liquid water) is required. This can be attained by means of detailed computer simulations, both macroscopically (relevant for appropriately delivering the dose) and at the nanoscale (important for determining the inflicted radiobiological damage). The energy lost per unit path length (i.e., the so-called stopping power) of carbon ions is here theoretically calculated within the dielectric formalism from the excitation spectrum of liquid water obtained from two complementary approaches (one relying on an optical-data model and the other exclusively on ab initio calculations). In addition, the energy carried at the nanometre scale by the generated secondary electrons around the ion’s path is simulated by means of a detailed Monte Carlo code. For this purpose, we use the ion and electron cross sections calculated by means of state-of-the art approaches suited to take into account the condensed-phase nature of the liquid water target. As a result of these simulations, the radial dose around the ion’s path is obtained, as well as the distributions of clustered events in nanometric volumes similar to the dimensions of DNA convolutions, contributing to the biological damage for carbon ions in a wide energy range, covering from the plateau to the maximum of the Bragg peak.

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“…In all these applications the accurate assessment of the electronic excitation spectra is a key factor, which can be accomplished by using ab initio simulations [2] or experiments [3]. Unfortunately, a long standing problem of bulk Ta 2 O 5 is to be characterized by polymorphism [4].…”

Section: Introductionmentioning

confidence: 99%

In search of the ground state crystal structure of Ta$_2$O$_5$ from ab-initio and Monte Carlo simulations

Pedrielli¹,

Pugno²,

Dapor³

et al. 2022

Preprint

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Tantalum oxides (Ta 2 O 5 ) are characterised by attractive physical and chemical properties, such as high dielectric constants and anti-reflection behaviour. Recently, Ta 2 O 5 nanoparticles have also been proposed as possible enhancers of the relative biological effectiveness in hadrontherapy for cancer treatment. In principle, their electronic properties can be accurately investigated from first-principles simulations. However, the existence of several stable polymorphs of these oxides represents a major difficulty in order to calculate and disentangle their respective spectral features. To assess this problem, we use linear-response time-dependent density functional to investigate the energy loss function Im(−1/¯ ), which is a unique fingerprint of the material, in the optical limit for various polymorphs. We show that the experimental reflection energy loss signals can be rationalized and interpreted by assuming that the γ-phase of Ta 2 O 5 represents the underlying structural model. We notice that both the inclusion of local field effects and spin-orbit coupling are crucial to compute the energy loss functions of this material. Finally, to further validate the γ-Ta 2 O 5 polymorph as a model for experimental tantalum oxide, we compute the reflection energy loss spectra using a Monte Carlo approach, finding an excellent agreement with the experimental data.

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Electronic excitation spectra of cerium oxides: from ab initio dielectric response functions to Monte Carlo electron transport simulations

Abstract: CeO2 partial/total density of states and electronic excitation spectrum from its valence levels.

Cited by 12 publications

References 86 publications

Unraveling Ce³⁺ detection at the surface of ceria nanopowders by UPS analysis

Unraveling Ce³⁺ detection at the surface of ceria nanopowders by UPS analysis

Energy Deposition around Swift Carbon-Ion Tracks in Liquid Water

In search of the ground state crystal structure of Ta$_2$O$_5$ from ab-initio and Monte Carlo simulations

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Electronic excitation spectra of cerium oxides: from ab initio dielectric response functions to Monte Carlo electron transport simulations

Abstract: CeO2 partial/total density of states and electronic excitation spectrum from its valence levels.

Cited by 12 publications

References 86 publications

Unraveling Ce3+ detection at the surface of ceria nanopowders by UPS analysis

Unraveling Ce3+ detection at the surface of ceria nanopowders by UPS analysis

Energy Deposition around Swift Carbon-Ion Tracks in Liquid Water

In search of the ground state crystal structure of Ta$_2$O$_5$ from ab-initio and Monte Carlo simulations

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Product

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Unraveling Ce³⁺ detection at the surface of ceria nanopowders by UPS analysis

Unraveling Ce³⁺ detection at the surface of ceria nanopowders by UPS analysis